1. Field of the Invention
The present invention relates to a storage system comprising a shared memory for providing access from a plurality of processing units.
2. Description of the Related Art
Large-scale storage systems are known that have a lot of nodes for coupling to upper-level apparatuses such as host computers to provide accessibility to data in any disk drive of the storage system from the host computer. In a storage system including a plurality of processors for increased performance, control information is shared among a plurality of the processors. To share the control information, a memory for storing the control information is shared or accessed by all processors in principle. Japanese laid-open patent application No. 11-232171, which is incorporated herein by reference, discloses a technology in which an address that has the possibility of being next accessed is predicted. Japanese laid-open patent application No. 2000-347937, which is incorporated herein by reference, discloses a storin control apparatus in which a processor accesses a shared memory. Japanese laid-open patent application No. 2001-306265, which is incorporated herein by reference, discloses a disk array control apparatus in which operand data is stored in a register in an external access control unit for controlling external access by the processor. Although each of these systems provides access to the shared memory by all of processors, a further speed-up will be difficult due to restriction such as a distance between the processor and the shared memory. Further, Japanese patent application No. 2005-083036, which is incorporated herein by reference, discloses a storage system.